The use of thin, radiation absorbing layer on a substrate as an optical recording medium operated by ablation of image areas is well known in the art. The expansion of the layer assembly to include reflective and/or interference layers is also known. The earlier examples of these used evaporated metal coatings on a substrate (see U.S. Pat. No. 3,560,994 and IEEE Journal QE-14, 487 (1978)). Later examples used organic materials as the absorber.
Vacuum-coated, light-absorbing layers of dyes or other absorbing organic compounds have been disclosed for ablative optical recording (U.S. Pat. No. 4,218,689). These however involve the costly vacuum-coating process and are not erasable/reusable.
Media for recording information by thermally altering the physical structure of a material are known. U.S. Pat. No. 3,475,760 describes such a medium for recording information as a thermal deformation pattern (doing so without requiring the formation of an electrical charge pattern on the medium). The medium is a 1 to 10 micrometer thick layer of a solvent-coated thermoplastic material on a support. The patent teaches that some thermoplastic materials, with, if necessary, pigments or dyes added to adsorb radiation strongly at the wavelength of a laser beam having a diameter of less than 10 micrometers, can be thermally deformed by that laser beam so that some of the thermoplastic material is displaced from the area illuminated by the beam to form ridges along the edges of that area. This deformation pattern retains its shape after the laser beam is "removed" and may be read by projecting the pattern onto a viewing screen as a Schlieren image, or viewing the image through Schlieren optics.
U.S. Pat. No. 4,139,853 describes a material for recording the information carried by a modulated laser beam comprising a support bearing a 0.5 to 10 micrometer thick recording layer comprising a thermoplastic polymer having dissolved therein up to 10 percent by weight of an organic dye which provides a specular density of at least 0.1 to the layer with respect to the wavelength of the recording laser. Such recording material is said to develop light scattering centers with a minimum increase of white light specular density of 0.2 with respect to the background when exposed to a light energy dose of at least 1.times.10.sup.6 erg/cm.sup.2 (0.1 watt sec/cm.sup.2) with a focused laser beam having a beam intensity of at least 1.0.times.10.sup.11 erg/cm.sup.2.sec (1.times.10.sup.4 watts/cm.sup.2). Information recorded on such material is read by scanning with the recording laser beam with its power reduced to about one tenth of that used for recording.
U.S. Pat. No. 4,364,986 discloses optical recording layers on a substrate in which the concentration of absorbing dye can be raised to very high levels (up to 94 weight %) while maintaining high clarity. The copolymer used as the thermoplastic binder is described as a 1:1 copolymer of methyl vinyl ether and maleic anhydride or a semi-ester of the copolymer and a low melting point monohydroxyalcohol. Ionic dyes are preferred to attain the high concentration levels.
U.S. Pat. No. 4,380,769 discloses that a dye-polymer layer can be thermally deformed by laser light absorbed by the dye, and read by a second laser not absorbed by the dye but scattered by the deformations. Very thin layers can then be used which enable high information density in the record to be achieved at high signal/noise ratio. One dye is disclosed (Iosol Red) which is capable of being coated out of solvent and has subsequent use in recording without any binder. (This dye is also known as CI Solvent Red 68 but no structure has been disclosed).
A paper entitled "Single Wavelength Optical Recording in Pure Solvent-Coated IR Dye Layers" by D. J. Gravesteijn, C. Steinbergen, and J. van der Veen (Philips, Endhoven) was published in Proceedings of SPIE, Vol. 420, page 327-331, which published the papers at a conference on Optical Storage Media in June 1983. This discloses layers of squarylium dye and of certain pentamethine ionic dyes which can be solvent-coated on suitable substrates to give layers of the order of 100 nm thick. These are shown to have good optical recording properties when used in the deformation mode.
Kokai JA59-45195, laid open Mar. 13, 1984, discloses hydrocarbon backbone polymers with pendent chromophores, e.g., azo, anthraquinone, indigoid, cyanine, etc. Polymers are thermoplastic and film forming, and are useful as thin coated layers for deformation optical recording.
Kokai JA59-62188, laid open Apr. 9, 1984, discloses various polymer backbones, e.g., polyester, polyurethane, polyamide, vinyl polymers, etc., with pendent phthalocyanine (preferably metal) chromophores. Polymers are thermoplastic and film forming, and useful as thin coated layers for deformation optical recording.
U.S. Pat. No. 4,365,012 discloses cyclic polyimides solution coated onto a substrate and used to form images by photochromism. No ablation or deformation of the coated layer is involved. These polymers are represented by the general formula ##STR1## where R is a divalent aliphatic group containing an electron donor function and n can be from 2 to 1000.
Offenlegungsschrift DE No. 3007296A1 discloses polymeric photochromic indigoid dyes in which the backbone is a hydrocarbon and the chromophores are pendent from it. The polymeric dyes are used for optical recording. No thermoplastic deformation is disclosed.
U.S. Pat. No. 4,241,355, in teaching ablative recording layers of vacuum evaporated phthalocyanine dyes, discloses that poly(chlorophthalocyanine) decomposed on heating and that copper poly(chlorophthalocyanine) did not evaporate at 400.degree. C.
U.S. Pat. No. 3,245,965 teaches that polyphthalocyanines and their metal derivatives are not solvent soluble and are not easily melted. Thin layers on a substrate are obtained by reaction of pyro-mellitonitrile at the surface.
Oligomeric dyes have been disclosed in U.S. Pat. No. 4,365,012 useful as photosensitive materials in optical recording devices.
Polymeric dyes per se are widely disclosed in the literature. Of particular prominence is their use as food colorings, and in the bulk or surface coloring of plastic objects and textile fibers.